Various trap designs were tested in Congo in order to assess their cost vs. effectiveness for the control of human trypanosomiasis vectors. These preliminary trials indicated that it is necessary to compare the different trap designs in several African countries. Furthermore, studies on the attractiveness of locally available fabrics must be carried out in order to make traps taking into account the sizes of locally available fabrics. At present, the ‘Vavoua’ trap is sail the most efficient but further investigations need to be carried out to reduce the cost of new traps without significantly affecting their efficiency. The ‘black/blue/black’ screen can be used successfully by rural communities in Congo for tsetse control.

In the forest zone of Côte d'Ivoire, Vavoua's traps and supports treated with pyriproxyfen® (Sumitomo) have been tested against Glossina palpalis palpalis. The supports were impregnated one time only at the dosage of 2 mg/cm2.

This juvenile hormone mimic acting as growth regulator has a good efficacy: apparent density was reduced by 87% after 2 months and was maintained at this level for 150 days; percentage of nulliparous females was equal to 0 between 40th and 120th days.

Pyriproxyfen may be recommended for the control of animal trypanosomiasis vectors—if it costs less than the insecticides; its slow effect on tsetse population does not favour its use for the control of human African trypanosomiasis which needs a drastic and immediate reduction of Glossina densities.

The diurnal resting sites of Glossina palpalis palpalis were studied from October 1981 to December 1982 in the human trypanosomiasis focus at Bouafle (Ivory Coast). A total of 1382 resting tsetse (970 males and 412 females), were found after 757 hr of search in their natural habitats.

At any season, over 80% of the flies were resting on lianas (Acacia pennata in particular), on coffee trees (Coffea indica) and on Eupatorium odoratum.

Almost all the flies showed a preference for resting on the underside of woody parts of plants selected. The heights of the resting sites ranged from 10 cm to 2.5 m above the ground and their diameters ranged from 0.1 cm to 8 cm. It must be stressed that both in the dry and in the rainy seasons, more than 50% of the flies rested below 50 cm from the ground and over 90% of these favoured stems and branches measuring less than 3 cm in dia.

In the vegetation surrounding villages or along the main access roads and bush pathways, G. p. palpalis were found resting at 1 m to 5 m from the edge of its vegetation habitat.

About 27% of flies were engorged or showed at least red blood meals in their guts. The catching of resting flies therefore, appears to be an excellent way of collecting fresh blood meals for identification of the natural vertebrate hosts of G. p. palpalis in the study area.

The practical interest of the study is discussed and recommendations made for the selective application of residual insecticides in the tsetse habitats to control the vectors of sleeping sickness in the Bouafle focus.

Ground spraying trials with different dosages of deltamethrin wettable poweder (NRDC 161) were carried out against G. palpalis (s.l.), vector of sleeping sickness, in January and November 1981 in the Bouaflé human trypanosomiasis focus, Ivory Coast. Three dosages have been tested: 60 g of active ingredient (a.i.) per ha at a concentration of 0.08% in January; and 20 and 12 g of active ingredient per ha in November at 0.027 and 0.016%, respectively. Each dosage has been applied once as a residual spray; spraying apparatus used was the atomiser Solo Port 423. The knock-down and short-term effects of the insecticide were very satisfactory: 90–98% reduction in apparent density of the vector was obtained during the first 2 months after treatment with all the three dosages applied. In the long term, 2–4 months after spraying, more than 95% reduction in apparent density of G. palpalis (s.l.) was achieved even with the lowest dosage of 12 g (a.i.)/ha. The highest dosage of 60 g (a.i.)/ha does not seem to increase significantly the persistence of the insecticide nor the mortality rate of the vector in the study area. In order to reduce the cost of a tsetse control programme and also to minimise insecticide impact on non-target organisms, it is therefore recommended that deltamethrin w.p. be applied at the lower dosage of 12 g (a.i.)/ha in residual ground spraying.